1. Field of the Invention
The present invention relates to an electronic device equipped with a connector for connecting an external device so as to supply, through the connector, the external device with a signal on which voltage is superposed; a transmission system for transmitting an output signal corresponding to an input signal from any signal transmission sections with which the external device and the electronic device are provided; and a method for determining a connection condition between the connector of the electronic device and the external device.
2. Description of Related Art
FIG. 1 shows an infrared optical transmission apparatus 200A as related art. This infrared optical transmission apparatus 200A is equipped with an infrared optical transmission section 201 which is configured, for example, with an infrared light-emitting diode etc. so as to output an infrared signal SIR and also with a connector, not shown in FIG. 1, for connecting an infrared optical transmission unit 300 having an infrared optical transmission section 301.
In this circumstance, when a connector (plug) 303, which is connected to an end of a connection cable 302 that is in turn connected to the infrared optical transmission unit 300, is connected to a connector (jack) of the infrared optical transmission apparatus 200A, a situation arises where a modulated RF signal, on which a DC power supply voltage is superposed, can be supplied from the infrared optical transmission apparatus 200A to the infrared optical transmission unit 300 and an infrared signal SIR that corresponds to the modulated RF signal can be output from the infrared optical transmission section 301.
FIG. 2 shows circuit configurations of the infrared optical transmission apparatus 200A and the infrared optical transmission unit 300.
The following will describe the circuit configuration of the infrared optical transmission apparatus 200A.
A DC power supply voltage DC1 of, for example, 12V obtained from a power supply circuit, not shown, is supplied to a regulator 202 from which a stabilized DC power supply voltage DC2 of, for example, 9V can be obtained.
An output side of the regulator 202 is connected to a collector of an NPN driver transistor 204(1), whose emitter is grounded, through a series circuit constituted of infrared light-emitting diodes 203(1, 1) through 203(n, 1). The output side of the regulator 202 is also connected to a collector of an NPN driver transistor 204(m), whose emitter is grounded, through a series circuit constituted of infrared light-emitting diodes 203 (1, m) through 203(n, m). Herein, n=3 and m=4, for example, are used. Thus, the n times m number of infrared light-emitting diodes 203(1, 1) through 203(n, m) constitute the infrared optical transmission section 201.
An amplifier 205 receives and amplifies a modulated RF signal MRF obtained from a modulation circuit, not shown. An output side of this amplifier 205 is connected to a base of each of the transistors 204(1) through 204(m). The modulated RF signal MRF is obtained, for example, by performing digital modulation on a carrier wave with audio data, image data or the like, and produced so as to have a constant amplitude.
An amplifier 206 also receives and amplifies the modulated RF signal MRF obtained from the modulation circuit, not shown. An output side of this amplifier 206 is connected to a connector (jack) 209 through a series circuit constituted of an output resistor 207 and a DC cut-off capacitor 208. Further, the output side of the regulator 202 described above is connected to the connector 209 via a RF cut-off inductor 210.
The following will describe operations of the infrared optical transmission apparatus 200A.
A stabilized DC power supply voltage DC2 obtained from the regulator 202 is supplied as power to the infrared optical transmission section 201. Further, the modulated RF signal MRF obtained from the modulation circuit is amplified by an amplifier 205 and then supplied as a drive signal to the base of each of the transistors 204(1) through 204(m). Accordingly, in response to the modulated RF signal MRF, the diodes 203(1, 1) through 203(n, m) emit light, so that an infrared signal SIR corresponding to the modulated RF signal MRF can be output from the infrared optical transmission section 201.
The modulated RF signal MRF obtained from the modulation circuit is amplified by the amplifier 206 and then supplied to the connector 209 through the series circuit constituted of the output resistor 207 and the DC cut-off capacitor 208. Further, the stabilized DC power supply voltage DC2 obtained from the regulator 202 is supplied to the connector 209 through the RF cut-off inductor 210. Accordingly, the modulated RF signal MRF on which the DC power supply voltage DC2 is superposed can be supplied to the connector 209.
The following will describe the circuit configuration of the infrared optical transmission unit 300.
An end of the connection cable 302 that is opposite to the end thereof to which the connector 303 has been connected is connected to one end of an RF cut-off inductor 304. The other end of this RF cut-off inductor 304 is connected to a collector of an NPN driver transistor 306(1), whose emitter is grounded, through a series circuit constituted of infrared light-emitting diodes 305 (1, 1) through 305(n, 1). This other end of the RF cut-off inductor 304 is further connected to a collector of an NPN driver transistor 306(m), whose emitter is grounded, through a series circuit constituted of infrared light-emitting diodes 305(1, m) through 305(n, m). Herein, n=3 and m=4, for example, are used. Thus, n times m number of infrared light-emitting diodes 305(1, 1) through 305(n, m) constitute the infrared optical transmission section 301.
Further, the end of the connection cable 302 that is opposite to the end thereof to which the connector 303 has been connected is grounded through a series circuit constituted of a DC cut-off capacitor 307 and an input resistor 308. A node between the capacitor 307 and the input resistor 308 is connected to a base of each of the transistors 306(1) through 306(m) through an amplifier 309.
The following describe operations of the infrared optical transmission unit 300.
When the connector (plug) 303 is connected to the connector (jack) 209 of the infrared optical transmission apparatus 200A, the end of the connection cable 302 that is opposite to the end thereof to which the connector 303 has been connected is supplied with the modulated RF signal MRF on which DC power supply voltage DC2 is superposed. For this reason, the DC power supply voltage DC2 appears at the other end of the RF cut-off inductor 304. This DC power supply voltage DC2 is supplied as power to the infrared optical transmission section 301.
Further, the node between the DC cut-off capacitor 307 and the input resistor 308 is supplied with the modulated RF signal MRF. This modulated RF signal MRF is amplified by the amplifier 309 and then supplied as a drive signal to the base of each of the transistors 306(1) through 306(m). Accordingly, the diodes 305 (1, 1) through 305(n, m) emit light in response to the modulated RF signal MRF, so that an infrared signal SIR corresponding to the modulated RF signal MRF can be output from the infrared optical transmission section 301.
FIG. 3 shows another infrared optical transmission apparatus 200B as related art. This infrared optical transmission apparatus 200B is equipped with a connector, not shown in FIG. 3, for connecting the infrared optical transmission unit 300 but, in contrast to the infrared optical transmission apparatus 200A described above, the infrared optical transmission apparatus 200B is not equipped with an infrared optical transmission section for outputting an infrared signal SIR.
In this circumstance, the connection cable 302 is connected to the infrared optical transmission unit 300 while the connector (plug) 303 that is connected to the end of the connection cable is connected to a connector (jack) of the infrared optical transmission apparatus 200B. In such a manner, a modulated RF signal on which a DC power supply voltage can be superposed is supplied to the infrared optical transmission unit 300 from the infrared optical transmission apparatus 200B. This gives rise to a condition such that an infrared signal SIR corresponding to the modulated RF signal can be output from the infrared optical transmission section 301.
FIG. 4 shows circuit configurations of the infrared optical transmission apparatus 200B and the infrared optical transmission unit 300.
The following will describe the circuit configuration of the infrared optical transmission apparatus 200B. This infrared optical transmission apparatus 200B has the same configuration as that of the infrared optical transmission apparatus 200A described above except the infrared light-emitting diodes 203(1, 1) through 203(n, m), the transistors 204(1) through 204(m), and the amplifier 205.
The following will describe operations of the infrared optical transmission apparatus 200B. The modulated RF signal MRF obtained by a modulation circuit, not shown, is amplified by the amplifier 206, and then supplied to the connector 209 through a series circuit constituted of the output resistor 207 and the DC cut-off capacitor 208. Further, the stabilized DC power supply voltage DC2 obtained from the regulator 202 is supplied to the connector 209 by way of the RF cut-off inductor 210. Accordingly, the connector 209 is provided with a modulated RF signal MRF on which the DC power supply voltage DC2 is superposed.
The infrared optical transmission system 300 has the same circuit configuration as the above-described configuration. Therefore, if the connector 303 is connected to the connector 209 of the infrared optical transmission system 200B, the end of the connection cable 302 that is opposite to the end thereof to which the connector 303 is connected is supplied with the modulated RF signal RFM on which the DC power supply voltage DC2 is superposed. Therefore, an infrared signal SIR corresponding to the modulated RF signal MRF is output from the infrared optical transmission section 301.
Japanese Patent Application Publication No. Hei 8-288909 has disclosed an apparatus for converting a video signal or an audio signal into an optical signal and transmitting it by means of a space, in which dissipation power can be saved by driving light-emitting means only when it is necessary for an optical signal to be transmitted. For example, if an AV pin plug is connected to an output terminal, a signal reproduced from a VTR block is output to outside through the AV pin plug, and at such a time, a microcomputer supplies an infrared transmission modulator and a light-emitting section with a power supply control signal that turns off the drive voltage.